Screw jack



Oct. 7, 1930. Jy'w. BA1-E .SCREW JACK Filed Jan. 5. 1927 26 Z5' if 70% Y2 sneets'shnt 1 J. W. BATE SCREW JACK Oct. 7, 1930.

Filed Jan. 5. 1927 2 Sheets-Sheet 2 7 J r. 4 0 2 2 2% l ||||1-:|l| .1.1.1M z l if. m m 1 J mm zwnmwww- ----+ii---,--m.\\ 4 M a 9 W j ,2E d J w2 w i 3 5 Patented Oct. 7, 193() i UNITED STATES PATENT oFFlcE JOHN W.RATE, or RACINE, wIsc'oNsIN, AssIGNoR 'ro WALKER MANUFACTURING COMPANY,F RACINE, WISCONSIN, A. CORPORATION OF WISCONSIN SCREW JACK Applicationled January, 1,927. Serial No. 159,107.

rlhis invention 'relates to screw jacks and particularly to those of thedouble lift type which are particularly adapted to be used onautomobiles having balloon tires. Such automobiles require a jack havinga very low initial height owing to the fact that when the tire is'deflated the axle is very close to the ground. At the same time thelarge size of the tire requires that the lift of the jack shall berelatively very large.

The invention is fully described in the fol* lowing specification andshown in the accompanying drawings, in which:

Figure 1 is a vertical sectional view through a jack embodying theinvention, the

jack being here shown in the fully lowered position;

Fig. 2 is a transverse section on the line 2 of F1g.1; v

Fig. 3 is a partial transverse section on the line 3 of Fig. 4; and

Fig. `4 is a view similar-to Fig. 1, but showing the outer screw in amid-position, the lnner'screw having been unscrewed by hand so. as tostand in its position of maximum lift w1th respect to the inner screw.

The embodiment illustrated comprises a hollow cast iron housing 1'0having a ledge` 11 upon which is supported aball thrust bearing 12, Vthelatter supporting in turn a nut 13. The nut. 1s retained in the top orthe housing by means of a screw 14 which :en-

gages anannular groove 15.

The, nut 13 carries bevel gear teeth 13v whlch engage the lteeth of abevel pinion 17.'

The latter is pinnedon a shaft 18,-which is journaled in suitablebearings in the housing and -has an outer end 19 which is squared orotherwise adapted to receive a suitable crank for turning the same.

The nut 13 is provided with internal screw y, threads which are adaptedto mesh with corresponding thr-eads on the outer screw V2U.v 'This screwis hollow andis provided at its upper end with internal threads 21 whichin turn are adapted to mesh with the threads of the inner screw 22. Thelatter threads stop at the lower end 23 so as to prevent this screwbeing withdrawn, while the upper end of the inner screw 22 is providedwith a cap 24 which is secured thereonby means of a pin 25.

The lower end of the housing is closed by l means of a plate 26 which issecured in place therein as by peening over the edg/e ofthe opening asat 10a. A bracket 27 is secured within the plate 26 and 'carries a pin28 on which is pivotally mounted the lower end of a lever 29, the upperend of the lever being pressed inwardly by means of a spring 30.

The upper end of the lever 29 carries an insert 31 which is thusnormally held in the longltudinal groove a in the outer screw. The lowerend of the screw 20 is provided with an annular ledge 32, the purpose ofwhich will later be explained.

In a mid-positionA of the outer screw 20, as' shown in Fig. 4, theinsert 31 is forced into the groove 20aby the spring 30,' therebypreventing the screw 20 from rotating. Uonsequently as the nut 13 isturned, itraises or lowers the screw 2O depending on which way the screwis turned. As the screw 20 is fed down the lower end of the screwfinally strikes the horizontal portion 29 of the lever 29. As the screwcontinues to descend it forces the lever `29 backfagainst the action ofthe spring'30 until the insert 31 is drawn back as shown in Fig. 1 sothat it clears the groove 20a. Further movement of the nut 13 1n thissame direction then carries the outer position of the outer screw 20. Itcan, however, beraised to the position here shown hy unscrewing thescrew 22 by hand.

With the parts in the position'as shown in Fig. 4, and the nut 13 beingturned in a direction to raise the outer screw 20. this l.

'screw' will be prevented from turning as has been heretofore explainedby the insert 31 which will remain in the groove 20 until the beveledenlargement 32 moves up under the insert 31. When' this occurs, theinsert 31 will be pushed back and will thereby permit the screw 20 toturn with the nut 13. As the asf ,fications screw 20 then continues toturn, the upper portion acting as a nut will in turn force the innerscrew 22 outwardly since it is heid by the load resting upon the cap 24.This inner screw which, up to this time has been within the outer screw20, is now fed'upwardly until stopped by the unthreaded bottom 23. y

The lowering operation is just the reverse of this. On turning the nut13 ina direction to lowerthe ack, the nut and outer screw 2O rotatetogether until the inner screw 22 strikes the top of the outer screw 2()as shown in Fig. 1(` and any further motion of the nut .y 13 in the samedirection causes the screw 20 to be fed through this nut.

Vhile I have shown and described but a single embodiment of vthisinvention, it is to be understood that it is capable of many modi-LvChanges therefore in the. construction and arrangement may be made whichdo not depart from the spiritand scope of the invention as disclosed inthe/appendedr claims.

Iy claim:

1. In a jack, a housing, inner and outer telescoping screw liftingmembers, a nut car- 'ried by. said housing for lifting the outerv screw,means for rotating said nut, and a spring-pressed elementv carried bysald houslng and adapted to engage one of said screws to yprevent itfrom rotating, said outer screw v y acting to render said elementinoperative at F i the lower end of the movement of said outer screw. l

2. In a jack, a housing, inner and outer telescoping screw liftingmembers, a nut carried by said housing for lifting the outer screw,means for rotating said nut, and a spring-pressed element carried bysaid housing and adapted to engage a groove in said outer screw to`prevent it from rotating, one of said screws acting to render said'element inoperative at the lower end of the movement of said outerscrew.

3.1111 a jack, a housing, inner and? outer telescoping screw liftingmembers, a nut lcarried by said housing for lifting the outer screw,means for rotating said nut, and a sprung-pressed element hingedlymounted 1n l said housing and adapted to vengagea groove in said outerscrew, said screw being adapted to force said element away from saidgroove as the screw approaches the lower end of its movement.

4;. In a jack, a housing, inner and outer telescoping screw liftingmembers, a nut car# ried by said housing for lifting the outer screw,means for rotating said nut, and a lever'hingedly mounted in the lowerportion of said housing and adapted to engage said outer screw toprevent it from turning, said lever having a portion lying in the pathof said outer screw so that said outer screw engagesrit .at theY lowerextremity of its movement to force said lever out of engagement withsaid outer screw.

5. In a jack, a housing, inner and outer telescoping screw liftingmembers, a nut carried by said housing for lifting the outer screw,means for rotatingv said nut. and a lever hingedly mounted in the lowerportion of said housing and having a nger adapted to engage alongitudinal groove in said outer screw to prevent it from turning, saidlever having a portion. lying'in the path of said outer screw so thatsaid outer screw engages it at the lower extremity of its movement toforce said lever out of engagement Vwith said outer screw.'

6. In .a device of the character set forth, a housing, inner and outertelescoping screw members, a nut journalled in said housing and adaptedto lift one of said screw, a movable element in said housing contactingwith one of'said screws and adapted to prevent rnF tation thereof duringits length of vertical travel, and means carried. by one of said screwsadapted to force said movable element out of contact with said screwwhen said screw is at the limits of its travel. y

In testimony whereof I have hereunto set my hand this 24th day ofDecember, 1926.

JOHN W. BATIC.

